Enterococci are Gram-positive cocci that are considered normal inhabitants of the gastrointestinal tract and the female genital tract. Enterococcus spp. are not particularly pathogenic in humans, but vancomycin-resistant enterococci have been increasingly identified as an important cause of hospital acquired infection. Vancomycin-resistant enterococci have been recognized as the second most common cause of hospital infection, exceeded only by E. coli. Enterococcus faecalis (85–90%) and E. faecium (5–10%) are the species of Enterococci most commonly isolated from the gastrointestinal tracts of humans and represent the majority of the vancomycin-resistant enterococci. 